Mini advanced font settings ignored in one book - embedded font?

I have a Kobo Mini and copied a few epub via calibre onto it. All free books.
In one book I can set the weight and sharpness of Georgia (kobo original). In another book the advanced settings are being ignored.

Can you tell me why the settings are not used?
Furthermore it seems the font is not used. Is this due to an embedded font? Is the embedded font always used or the user settings?